Lesson Notes By Weeks and Term v5 - Grade 8

Lesson Video

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Performance objectives

• Define atom, element, proton, neutron, and electron.
• Draw diagrams of atoms for the first 20 elements.
• Explain how proton number (atomic number) identifies an element.
• Describe the arrangement of the Periodic Table.
• Identify metals, non-metals, and metalloids.

Lesson summary

This week, we delve into the fascinating world of atoms and how they are organized in the Periodic Table. Understanding atomic structure is fundamental to understanding all matter around us, from the air we breathe to the food we eat. The Periodic Table is a vital tool for scientists, organizing elements based on their properties and helping us predict how they will behave. Imagine trying to build a house without knowing the properties of wood, bricks, or cement! Similarly, understanding atomic structure and the Periodic Table allows us to understand the "building blocks" of the universe and how they interact.

Lesson notes

2.1 Atoms: The Building Blocks of Matter Everything around us is made up of matter. Matter is anything that has mass and takes up space. The smallest unit of an element that retains the chemical properties of that element is called an atom. Atoms are made up of three subatomic particles: Protons: Positively charged particles located in the nucleus (center) of the atom. The number of protons determines what element the atom is.

Neutrons: Neutral (no charge) particles also located in the nucleus. Neutrons contribute to the mass of the atom.

Electrons: Negatively charged particles that orbit the nucleus in specific energy levels called shells. Think of the atom like a mini solar system. The nucleus (protons and neutrons) is like the sun, and the electrons are like the planets orbiting around it. 2.2 Elements and Atomic Number An element is a pure substance made up of only one type of atom. For example, gold (Au) is an element made up of only gold atoms. Oxygen (O) is an element made up of only oxygen atoms. The atomic number of an element is the number of protons in the nucleus of an atom of that element. The atomic number defines the element. For example, all atoms with 6 protons are carbon atoms, regardless of how many neutrons or electrons they have. The atomic number is typically found above the element symbol on the Periodic Table.

Example: Hydrogen (H) has an atomic number of 1, meaning it has 1 proton. Oxygen (O) has an atomic number of 8, meaning it has 8 protons. Iron (Fe) has an atomic number of 26, meaning it has 26 protons. 2.3 Drawing Atomic Structures (Bohr Diagrams) We can represent the arrangement of protons, neutrons, and electrons in an atom using a Bohr diagram.

Here's how: Determine the number of protons, neutrons, and electrons: The number of protons is equal to the atomic number. In a neutral atom (no overall charge), the number of electrons is also equal to the atomic number. To find the number of neutrons, subtract the atomic number from the mass number (which you will learn about later but for now, we can approximate with a simple guide - Hydrogen is around 1, Helium is around 4, Lithium around 7, Beryllium around 9, Boron around 11, Carbon around 12, Nitrogen around 14, Oxygen around 16, Fluorine around 19, Neon around 20, Sodium around 23, Magnesium around 24, Aluminium around 27, Silicon around 28, Phosphorus around 31, Sulfur around 32, Chlorine around 35.5, Argon around 40, Potassium around 39, Calcium around 40).

Draw the nucleus: Write the number of protons (p+) and neutrons (n0) inside a circle representing the nucleus.

Draw the electron shells: Draw circles around the nucleus representing the electron shells.

Fill the electron shells: The first shell can hold a maximum of 2 electrons. The second and third shells can each hold a maximum of 8 electrons. Electrons fill the shells from the innermost shell outwards.

Example 1: Oxygen (O) Atomic number = 8 --> 8 protons, 8 electrons Approximate mass number = 16 --> 16 - 8 = 8 neutrons Nucleus: 8p+ , 8n0 Electron Shells: 2 electrons in the first shell, 6 electrons in the second shell.

Example 2: Sodium (Na) Atomic number = 11 --> 11 protons, 11 electrons Approximate mass number = 23 --> 23-11 = 12 neutrons Nucleus: 11p+ , 12n0 Electron Shells: 2 electrons in the first shell, 8 electrons in the second shell, 1 electron in the third shell. 2.4 The Periodic Table The Periodic Table is an organized arrangement of all known elements based on their atomic number and similar chemical properties. It's like a map of all the different kinds of atoms in the universe!

Arrangement: Elements are arranged in order of increasing atomic number (from left to right and top to bottom).

Groups (Columns): Elements in the same vertical column (group) have similar chemical properties because they have the same number of electrons in their outermost shell (valence electrons).

Periods (Rows): Elements in the same horizontal row (period) have the same number of electron shells. 2.5 Metals, Non-metals, and Metalloids The Periodic Table can be divided into three main categories of elements: Metals: Located on the left side of the Periodic Table (except for Hydrogen). Metals are generally shiny, malleable (can be hammered into sheets), ductile (can be drawn into wires), and good conductors of heat and electricity.

Examples: Iron (Fe), Copper (Cu), Gold (Au), Aluminium (Al).

Non-metals: Located on the right side of the Periodic Table. Non-metals are generally dull, brittle, and poor conductors of heat and electricity.

Examples: Oxygen (O), Nitrogen (N), Sulfur (S), Chlorine (Cl).

Metalloids (Semi-metals): Located along the staircase line that separates metals and non-metals. Metalloids have properties of both metals and non-metals. Their conductivity can be controlled, making them useful in electronics.

Examples: Silicon (Si), Germanium (Ge).